Effect of commercial formulation of four organophosphorus insecticides on the ovaries of a freshwater teleost, Mystus vittatus (bloch)--a histological and histochemical study

The chronic effect of an exposure to a sublethal concentration of commercial formulation of 4 organophosphorus insecticides such as birlane (chlorfenvinphos), gardona (tetrachlorvinphos), phosdrin (mevinphos) and malathion on midvitellogenic ovaries of Mystus vittatus was investigated using several histological and histochemical techniques. The loss of stage II and III oocytes accompanied by a significant decline in gonadosomatic index was recorded. The vitellogenesis in treated fishes was ceased as the oocytes did not advance to further stages as evidenced by the absence of lipid yolks and the lack of a PAS positive follicular layer. The RNA content of remaining stage I oocytes of exposed fishes resembled that of the stage I oocytes of the control fishes. The absence of delta 5-3 beta-hydroxysteroid dehydrogenase suggested the lack of steroidogenesis. Reduced glucose-6-phosphate dehydrogenase activity was also observed. The significance of these observations has been discussed in light of available literature.